The present invention applies to studs and clips for retaining rails to a rail supporting surface.
Rail clips (cleats) and retaining members of many configurations have been heretofore proposed. Some of these combinations and configurations have been somewhat successful but all fall short of the ideal rail retaining combination.
There are many requirements of a satisfactory rail retaining combination. Low cost and simplicity of operation are of great significance. Generally, a two piece combination is preferable from the standpoint of both cost and simplicity.
Of great importance in a rail retaining combination is that the clip provide the required rail retaining pressure without overstressing of the clip which would result in ultimate fracture and failure of the clip. It is additionally desirable that the combination provide a means by which rail overturn in extreme rail loading conditions can be avoided.
Another desirable feature of a rail retaining combination is that the device provide a low profile. This is necessary to provide clearance for such equipment as ballast regulators, snow plows and certain other machinery used upon the rails.
Another requirement of a desirable rail retaining combination is that, while the clips may be inserted or put into position without sophisticated equipment, it should resist disengagement by such means as vibration or vandals. Additionally, during installation of the clip, the design should be such that overdrive and thus overstress of the clip can be avoided.
In addition to providing the necessary rail hold-down pressure, it is also a desirable feature of an ideal rail retaining combination that the clip resist rail creep, i.e. longitudinal movement of the rail.
A further desirable feature of an ideal rail retaining combination is that the combination be capable of use in original installations or to retrofit existing installations. In the latter case, it is particularly important that the combination be a part of a system of installation which can be utilized with tie plates and rails of differing manufacture and configuration while using a standardized set of components.
Many clips which have been used heretofore have been formed from resilient plate which has one end bearing against the tie and the other against the rail foot, while a pin, bolt head or the like loads the central part of the clip. With this arrangement, however, the clip size is considerable and its stress is very high for a given spring rate.
Some designs have reduced the spring rate of the clip by imparting the loading to a clip having a return configuration something after the style of a "hairpin". An example of this design is shown in U.S. Pat. No. 3,451,621 to De Splinter which discloses a generally hairpin shaped clip which bears against the foot of the rail at one end and wherein the pressure is applied by a pin against the return end. However, the height of this clip is considerable and creates an interference with equipment upon the rails. Additionally, the clip involves the use of secondary fixing means which adds to the cost and complexity of the combination.
Another design of rail clip which utilizes a two part combination is disclosed in U.S. Pat. No. 4,067,495 issued to Portec. This arrangement is a single knock-on clip but the clip extends in a direction longitudinal to the rail and consequently is subject to serious disabilities such as rail creep. Additionally, the Portec device is made of rod having a substantially constant cross-sectional shape and the strain is much greater at the center than near the end such that optimum use of material is not achieved. Further, the Portec clip can be relatively easily dislodged, for example by vandals, with consequential hazard with respect to rail displacement.
U.S. Pat. No. 3,831,842 to Tamura discloses the use of a threaded member close to the intermediate portion of a hairpin type clip. Although the clip is of the general hairpin shape, it really functions in much the same way as the so-called flat plate clips.
Other disclsures of hairpin type clips are in British patent No. 968,128 issued to Rigby and in German patent No. 657,980 issued to Lossl. The structure of the British patent has several shortcomings. Among these is that the clip operates in conjunction with a U-shaped anchor which is driven into the cross tie and which is susceptible of varying heights to create variations in rail loading. Additionally, the U-shaped spike is susceptible of being withdrawn or loosened from its holding position. Additionally, the configuration of the clip in the British patent and its cooperation with the rail spike is susceptible to rotation thus being susceptible to rail creep. Another problem with the British patent is that, during insertion, there is no guard against overdriving and overstressing of the clip. Furthermore, the spacing of the upper and lower members and their configuration will permit the rail to rise out of the recess into which the rail is positioned thus permitting rail overturn. The British clip is further unsuited for use with metal rail plates which are the more prevalent configuration.
The rail clip combination shown in German patent No. 657,980 likewise has many drawbacks. The German clip combination must be utilized in conjunction with a rail plate which has formed integral therewith the retaining member. This is an extremely expensive combination. Additionally, the spacing of the upper and lower members is such that the rail will become any lockup occurring in the clip and may thus permit rail overturn. The German clip configuration is not susceptible to retrofit to existing rails but must be with newly replaced tie plates. Further, the heel configuration of the rail clip in the German patent is of a type that does not provide for ultimate control of the bending moment in the clip to achieve optimum rail engaging pressure.